A sheave, or grooved wheel, is used in many applications which require support of running cables or lines. Sheaves are commonly used in connection with wells, such as gas wells, oil wells, and water wells. Sheaves are also used in cable stringing operations. While much of the following discussion will refer to the oil and gas well industry, it will be appreciated that the invention disclosed herein may be used in a variety of applications that use sheaves.
Wells, such as gas wells, oil wells, and water wells that are created by drilling a deep, narrow hole in the ground and then cementing or otherwise securing a hollow, tubular casing within the hole. The well head is the portion of the casing exposed above the ground surface. A pump or valve is attached to the well head to control the flow of fluid or gas from the well.
It is frequently desired to run various types of tooling down the casing. Such tooling can include cameras, vibrators, explosives, various sound generators, and equipment for cleaning the interior of the casing. To facilitate lowering of the tooling within the casing, a wireline is used. The wireline must be able to withstand the highly corrosive environment that is commonly encountered within conventional gas and oil wells. Furthermore, the wireline must be sufficiently strong to withstand the tensile force placed on the wireline when the tooling is lowered hundreds and even thousands of feet within the casing. In addition, the type of wireline used is also dependent upon the type of tooling used. For example, some toolings require that the wireline carry an electrical current for powering or sending signals back from the tooling.
Due to the above requirements, the wireline can be extremely expensive, even up to several dollars a foot. Most wireline is comprised of stainless steel or other non-corrosive metal. Examples of conventional wireline include coaxial cable, E-line which is an armor cable with one or more conductive lines on the inside, and slick line which is a solid line often made of carbon steel.
During operation, a large continuous spool of wireline is brought to the well site. Although the wireline is relatively flexible, the wireline must be fed into the casing in such a fashion as to avoid kinking the wireline. Kinking can potentially damage or break the wireline. Furthermore, the wireline must facilitate smooth and easy lowering and raising of the tooling within the casing.
In a typical wireline operation, the cable is deployed from a winch cable reel through a first rigging sheave located on the drilling rig floor. This sheave is called the floor sheave, and the line goes upward from it to a second sheave suspended from a block on or near the center of the top of the drilling derrick. This second sheave is called the top sheave, and the line descends from it downwardly into the borehole.
Both the floor sheave and the top sheave include a freely rotatable wheel having a groove formed around the circumference thereof. The groove is configured to receive and retain the wireline. The wireline is drawn around the wheel of the lower sheave and then drawn over the wheel of the top sheave assembly. The wireline is laid within the groove of the wheels to prevent the wireline from sliding off the wheels. The free end of the wireline is attached to the tooling which is then lowered down into the casing. Typical examples of both floor sheaves and top sheaves are sold by the Wireline Technologies, Inc. located in Utah.
One problem associated with sheaves relates to their size. Specifically, most sheaves are generally heavy and difficult to move/transport. A typical sheave having a diameter of 20 inches weighs at least 60 pounds, and a typical sheave having a diameter of 36 inches weighs about 180 pounds. Such weight of the sheaves means that workmen who must carry these sheaves often experience injuries to their backs or other body parts that are caused by carrying this heavy equipment. Likewise, because the sheaves are heavy, workers will often drop or mishandle the sheave during transport. Such mishandling of the sheaves can cause serious and costly damage to the sheave itself, to the workers, and/or to other property.
There are frequent occurrences in which the tooling may accidentally get caught or momentarily stop as it travels down the casing. At these times, slack is produced in the wireline. This slack can cause the wireline to “jump” out of the groove on the wheel of the sheave assembly. Should the tooling then drop, the wireline and sheave assembly can be both badly damaged. On occasion, jumping of the wireline off of the sheave wheel can result in wireline breaking, thereby causing the tooling to freely fall to the bottom of the well. Not only is it extremely expensive to repair broken wireline, but there is extensive down time and expense in fishing the tooling from the bottom of the well. Furthermore, jumping and/or breaking of the wireline creates a hazard to the surrounding workers that are lowering the tooling
Accordingly, there is a need in the art for a new type of a sheave that addresses one or more of the above-referenced problems. Specifically, there is a need in the art for a new sheave that is lighter and easier to use and transport. Likewise, there is a need in the art for a sheave that will prevent a user's hands, clothing, limbs, from contacting and/or being injured by the cable. Further, there is a need in the art for a sheave assembly that will prevent the wireline from “jumping” out of the groove on the wheel of the sheave assembly. These and other advantages are disclosed by the present embodiments.